The kind of welding torch to which the invention relates is coupled to a number of services, including: a means for conveying electrical energy to the welding tip, and for producing an arc; a means for advancing welding rod progressively into the arc; and a means for supplying shielding gas, such as carbon dioxide or argon; to the arc, which serves to prevent oxidation at the arc.
The welding torch may be a component of an automatically guided welding head, or the torch may be designed to be held in the hand, in which case usually the torch including an operable switch means for controlling the welding rod advancer and the electricity supply to the arc. The welding torch may or may not also be coupled to a fume hood and vacuum extraction system.
One of the problems of welding torches is to keep the torch cool, and water-cooled welding torches are currently in widespread use. The manner in which the cooling jacket is arranged on the torch in the conventional designs however, in many cases has proved unsatisfactory.
It is recognised that the water jacket should be as close to the arc as possible, since the excessive heat comes of course from the arc. The more of the torch in the torch that is allowed to become hot, the more troublesome the cooling problem.
One particular problem that arises when the torch is allowed to overheat lies in the electrical insulation material present in the torch. This is generally of plastic material, for example Teflon (trademark), which can deteriorate if overheated. The water cooling jacket therefore should be close enough to the arc that the jacket prevents excessive heat being transmitted to the insulation.
It is recognised that the water jacket must not be allowed to leak. If droplets of water find their way into the weld, the strength of the weld can be seriously impaired.
Thus, the water jacket should extend in the axial sense as far forward as possible in the torch, towards the arc. It is recognised also that the water jacket should be close-in, radially, to the components surrounding the welding wire near the arc.
It is the general practice in torch design to run the wire through a nose-piece, which serves to guide and locate the welding wire immediately prior to the wire entering the arc. Apart from the wire itself, this nose-piece is the component of the torch that lies closest to the arc, and it is recognised that the water in the water jacket should directly touch the material of the nose-piece, if cooling is to be most effective. Most torches include a shroud for directing the gas over the arc; in cooling the torch, it is of little use, for example, to place the water jacket outside this shroud. Some previous designs of water cooled torch in fact have placed the water jacket outside the shroud, or outside the insulation; effectively useless as such measures are, they illustrates the extent to which it is desired to keep the torch cool.
The anti-oxidation or other weld-protecting or weld-enhancing gas approaches the nose-piece via a gas feed tube, and then spreads out around and over the nose-piece. The nose-piece is formed with gas-spreading-holes for thus conducing the gas. The design of the water jacket must take into account the fact that the exit-mouths, through which the gas emerges around the nose-piece, of course cannot be allowed to be compromised by the presence of the water jacket.
The invention is concerned with a design of the nose-piece in which all these varying requirements are accounted for an co-ordinated, and yet in which the nose-piece is cooled effectively.